Project Summary/Abstract Epidemiologic evidence has established obstructive sleep apnea (OSA) as a risk factor for Alzheimer?s disease (AD). However, the mechanisms of this increase in AD risk remain unclear. Three potentially AD-relevant clinical features of OSA include severity of hypoxemia, global sleep fragmentation, and local deficits in memory-relevant sleep oscillations, i.e. slow waves and sleep spindles. These clinical features of OSA have been independently linked to amyloid and tau burden and accumulation, medial temporal lobe (MTL) degeneration, and MTL- dependent memory impairment?all hallmark biomarkers of AD. However, it remains unclear how each of these features relate to AD pathophysiology or MTL-dependent memory decline in patients with OSA. The overarching research objective of this proposal is to address these unknowns. The proposed specific aims are to determine whether distinct global and local OSA features are associated with 1) cortical amyloid burden, 2) MTL tau burden, and 3) degeneration of specific MTL brain circuits supporting multiple forms of memory known to depend on sleep and be vulnerable to AD pathophysiology. The proposed aims will be supported by leveraging existing resources, and collecting high density electroencephalography (hdEEG, 256 channels) sleep recordings in cognitively normal older adults (60-85 years) undergoing positron emission tomography (PET) to assess amyloid and tau burden, as well as ultrahigh resolution magnetic resonance imaging (uhr-MRI) of MTL structure. The proposed study will therefore capitalize on an opportunity to examine how OSA relates to AD pathological burden, MTL structure and function, and memory in an unprecedented level of detail and breadth. This is congruent with both my short and long-term career goals. Specifically, I plan to generate research proposals seeking funding to uncover the impact of distinct forms of sleep disturbance on circuit and molecular mechanisms of AD pathogenesis in humans. This will support my efforts to establish a clinical research program evaluating i) the contribution of sleep disturbance to the onset and progression of various forms of neurodegenerative disease across clinical stages, ii) the utility of sleep-based biomarkers to predict dementia onset and aid differential diagnosis between dementias, and iii) the utility of targeted sleep-based interventions to arrest cognitive decline associated with AD and related dementias. This research proposal and my long-term career goals are supported by my training plan overseen by my mentoring team which includes experts in hdEEG, uhr-MRI, MTL-dependent memory circuit function, PET methods in the context of aging and AD?including amyloid and tau PET, clinical aspects of sleep disorders, geriatric psychiatry, and neurodegenerative disease, and clinical trial design and implementation in the context of sleep disorders and AD. The proposed training plan includes structured mentoring on each of these topics and participation in a clinical research certificate program, as well as a course focused on clinical trials in AD. By establishing this research program, I hope to develop sleep-based approaches to reduce risk, delay onset, and slow progression of dementia and age-related cognitive decline.